Global sea levels could rise by almost 6ft by 2100 – twice as much as had previously been predicted – threatening major cities and displacing hundreds of millions of people, a study published Monday warned.
The upper limit for sea level rise by 2100 has previously been estimated between 1.7 and 3.2ft. – the range given in the fifth assessment report from the Intergovernmental Panel on Climate Change (IPCC), the leading international body for the assessment of climate change, in 2013.
But many scientists believe that was a conservative estimate. The rate of glacier melt in Greenland and Antartica is accelerating, and the authors of the report say current prediction models don’t account for significant uncertainties in how melting ice sheets could affect sea level rise.
To get a better understanding, an international group of researchers compiled a “structured expert judgement study,” using expert understanding of what is happening to glaciers to predict a broader range of possibilities than those considered in the IPCC report.
The researchers estimate that, if emissions of greenhouse gases like carbon dioxide continue to grow unchecked, causing global temperatures to increase by about 5°C over pre-industrial levels, sea levels in 2100 would be 1.6 to 5.8ft higher than they are today. There is around a 5% chance we would hit the upper end of that range, the study said.
In the worst-case scenario, 691,120 square miles of land – around seven times the size of the United Kingdom – could be swallowed up by the sea. Large parts of low-lying countries like Bangladesh would become uninhabitable, while critical areas for food production would be lost. Major cities, including New York and London, would also be threatened.
Such land loss would cause the displacement of around 187 million people. “To put this into perspective, the Syrian refugee crisis resulted in about a million refugees coming into Europe,” the study’s lead author, Professor Jonathan Bamber of the University of Bristol, told the BBC. “That is about 200 times smaller than the number of people who would be displaced in a 2m sea-level rise.”
There is still time to prevent the more extreme scenarios of sea level rise, the study stressed. If we manage to limit global temperature increase below 2°C, in line with the Paris Agreement, the researchers estimate a sea level rise of 0.8 – 2.7 ft by 2100.